Posted
by
Soulskill
on Tuesday November 27, 2012 @02:25PM
from the regift-them-to-spacex dept.

astroengine writes "NASA has begun surveying scientists on what they would like to do with two Hubble-class space telescopes donated to the civilian space agency by its secretive sibling, the National Reconnaissance Office — which operates the nation's spy satellites. But the gifts have some formidable strings attached, including costs to develop instruments and launch the observatories. The telescopes, though declassified, also are subject to export regulations. 'We need to retain possession and control,' NASA's astrophysics division director Paul Hertz told Discovery News. 'That doesn't preclude us from partnering (with other countries). It just sets boundaries on the nature of the partnership.' NASA also isn't allowed to use the telescopes for any Earth-observing missions. Topping the list of possible missions for the donor hardware is a remake of NASA's planned Wide-Field Infrared Survey Telescope, known as WFIRST. The mission, estimated to cost between $1.5 billion and $2 billion, is intended to answer questions about dark energy, a relatively recently discovered phenomenon that is believed to be speeding up the universe's rate of expansion."

I don't know where I found out, but I knew soon after Hubble that the more were made for spy missions.

During the hearings over the Hubble Mirror fiasco, at least one NASA official admitted that the NRO [wikipedia.org] had warned them to calibrate the mirror carefully. Apparently, the spooks had made a similar error years earlier. Unfortunately, NASA did not heed the warning.

Stereo imaging has the added benefit of allowing the removal of glare from images, besides the cool 3D effect... Glare removal is especially helpful in viewing planets as they cross their sun. I think there's some land based telescopes that have or are attempting this.

I think you have that wrong way round, the Hubble mirror is the size it is because Lockheed (prime) could build it cheaper if it was sized the same as satellites they were already building. See wikipedia article on kh-11http://en.wikipedia.org/wiki/KH-11_Kennan [wikipedia.org]these were 2.4m space telescopes first launched in 1976, same prime as Hubble.

That's why Hubble was useful in the first place. As a telescope, it's not that impressive - far bigger and fancier ones exist. What sets it apart is that it is above all that atmospheric interference.

Well, not quite... the adaptive optics on modern ground-based telescopes can deal with much of the problems associated with atmospherics. The real win with Hubble is that a) it can look in wavelengths that are heavily attenuated by the atmosphere (Think UV and Infrared) and b) it can stare at a target, continuously, for very long periods of time. Earth-based telescopes are (obviously) limited to observing at night, while Hubble can continuously observe a large portion of the sky on a continual basis (24 hours, 36, whatever). This is especially important when you're trying to observe extremely dim targets who's brightness can be measured in photons per minute.

The telescopes in question are not "surplus": it consists of never finished hardware from the aborted optical component of FIA (Future Imagery Architecture). This optical FIA component, intended to replace the Keyhole system, was scrapped because of massive budget overruns. Part of the hardware was already built by that time, and that is what now has been donated to NASA. It never were complete telescopes, let alone "surplus"telescopes.

You don't need two telescopes to do 'stereo'. You can use the fact that the telescope is moving in space [wikipedia.org].

Unless you want to do interferometry. I don't know if long base optical interferometry is feasible. I know that the VLT in Chile is designed to do it but that they had a hell of a time to calibrate it. I would be beyond awesome to have those two babies in opposite solar orbits doing optical interferometry. Well, I'm probably dreaming as it would mean maintaining them fixed in respect to one another to one quarter wavelength of observed light... Or somesuch.

You're not going to get enough parallax on something as distant as a galaxy to be useful for stereo imaging. If you place these in Earth orbit, on opposite sides of the Earth, you're looking at on order 10000 km separation. The distance to the Canis Major Dwarf Galaxy (let's call that the nearest one) is 25,000 ly, or on order 10^17 km. That gives you a parallax of 20 nano-arcseconds. Hubble's diffraction limited resolution is 50 milli-arcseconds. (Interferometry won't help here, since we're trying to compare two distinct images from individual telescopes).

There are closer nebulae. The Orion nebula is only 1300 ly away, so we're looking at a parallax of 0.2 micro-arcseconds. Still not enough.

If, as another poster suggested, we put them at L4 and L5 (Sun-Earth), we're talking more like a few times 10^8 km separation. So that puts us in the few milliarcsecond range for the Orion nebula. Not quite good enough for visible light, but UV could work.